1. Field of the Invention
The present invention relates to lanthanide rare earth series cryptate salts. In particular the present invention relates to trivalent lanthanide cryptate salts which are highly stable in polar solvents, such as water. The invention also relates to a novel process for forming metal cryptate coordination compounds in general.
2. Description of the Prior Art
The prior art has described the preparation of mono- and divalent alkali metal and alkaline earth metal cryptate coordination compounds in J. Phys. Chem. 81, 760 (1977); J. Am. Chem. Soc. 97, 7382 (1975) Structural Bonding Berlin 16,2 (1973) and J. Am. Chem. Soc. 97, 6700 (1975). Such metal cryptate compounds are relatively labile in aqueous solution and exchange with non-encryptated or aquated ions or merely dissociate over relatively short periods of time (a few minutes or less).